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Merck Joins Bristol, Genentech in Great Cancer Immunotherapy Race

similar for patients who previously got an immunotherapy, and those who hadn’t.

While tumor shrinkage rates can suggest a drug is working early on, they don’t mean much if the tumors find a way to bounce back quickly and spread again. But the Merck drug, like other immunotherapies, showed an intriguing ability to generate long-lasting tumor shrinkage rates. Researchers still don’t know how long the responses will last, but the patients have been followed for a median time of 11 months, and not enough have seen their disease worsen to provide a valid estimate of how long the drug works.

“These are clearly much more sustained responses than are seen with targeted agents or chemotherapy. That’s what makes this class such an impressive class,” Rubin says. “Presumably the reason it’s happening is you are re-training the immune system to fight cancer, and it becomes more difficult for the cancer to avoid that. Tumors are dynamic and can change, but the immune system is dynamic and can also change. It’s difficult for the cancer to escape that.”

Any time a drug works to stimulate the immune system, there’s a chance it can go too far, damaging healthy tissues, and causing autoimmunity. Most of the drug-related adverse events in this Merck study were mild to moderate, and included fatigue (30 percent of patients), rash (21 percent), pruritis /itching (21 percent), and diarrhea (20 percent). There were six mild to moderate cases of pneumonitis, a worrisome inflammatory condition of the lungs. The overall rate of side effects was lower than what researchers have seen with prior immunotherapy, like Bristol’s ipilimumab (Yervoy).

Based on the results, Merck is moving ahead with four new clinical trials that are enrolling 600 patients. One will test the Merck drug in patients with advanced melanoma, and another study will enroll patients with non-small cell lung cancer. The company is also running studies for a tough-to-treat form of breast cancer, bladder cancer that has spread, and head and neck cancer.